Current stroke therapies approved for human use are limited. The one drug clinically available, the thrombolytic agent tissue plasminogen activator (t-PA), is indicated only if administered within 4.5 hours of symptom onset and carries with it a significant risk of intracranial hemorrhage. Consequently, only a small percentage of patients receive this therapy. Emerging data suggest that post-ischemic oxidative stress and inflammatory mediators contribute to brain injury and expansion of the ischemic lesion. As the inflammatory response is delayed (hours to days), it is an attractive target for therapeutic intervention. Inter-alpha inhibitor proteins (IAIP) are complex proteins (250 and 125 kDa) circulating in blood, which consist of multiple subunits. In Japan and China, one subunit (the light chain, also known as bikunin) has been isolated from urine and is used clinically to treat acute pancreatitis and other inflammatory diseases. However, the half-life of this subunit is very short (3-10 min), requiring large amounts of protein and constant intravenous infusion. We propose to evaluate the blood-derived complexes form of IAIP (half-life of 8-12 hrs.) as a potential neuroprotective agent, as this form is more feasible for clinical use. This formulation may also have additive protective effects due to the presence of other subunits (the heavy chain) in the complex. Preliminary work in our lab using exogenously administered blood-derived human IAIP at a dose of 30mg/kg (a dose that has shown protection in sepsis) found that IAIP is strikingly neuroprotective after experimental stroke in young adult mice. Infarct volumes are reduced and functional outcomes improved even when IAIP was given six hours after ischemic onset. We have now shown that the protection is sustained at 30 days, and that this agent is also protective in aged animals. Based on these very promising initial results we propose to systematically determine the optimal dose, examine the pharmacokinetics, and directly evaluate brain and serum levels of IAIP (Aim1). We will determine if neuroprotection and behavioral improvements are sustained at chronic (1 and 3 month) endpoints in aged mice of both sexes (Aim 2) and determine if protection is also seen in an embolic model of stroke (Aim 3). These studies were designed in response to the NINDS Exploratory/Developmental Projects in Translational Research (PAR13-023) program.